1. Field of the Invention
This invention relates to a process for operating sub-zones of a digital T.D.M. telecommunications network for long distance traffic wherein, on the wide-band transmission lengths which connect the exchanges there are transmitted information blocks, each of which blocks comprise items of information emanating from subscriber groups and which can be identified either by a preceding block address or by the sequence of block occurrence.
2. Description of the Prior Art
In the area of pulse code modulation (PCM) time divisional multiplex (T.D.M.) end exchanges it is known in the art, for example from U.S. Ser. No. 497,293, now U.S. Pat. No. 4,011,412 to transmit, on a common transmission line, from the end exchange, items of information which are each preceded by a subscriber address and which are taken up by the addressed subscriber station as a result of the receipt of this subscriber address. The subscriber stations subsequently emit the items of information which they are to transmit, in that they modulate this information onto an unmodulated bit group arriving from the end exchange following their own address and forward this bit group in the direction of transmission. The described processes take place in channel time slots allocated by the end exchange. The expense of individual subscriber devices in order to achieve a correctly timed operation of the subscriber end stations can, in this manner, be kept very low. If, in spite of the use of a wide-band transmission medium, for example in the form of a glass fiber line, the transmission of subscriber addresses occupies too large a part of the available transmission band, which can be the case when types of information other than telephone information are additionally transmitted on the transmission line, for example broadcast information, television information in association with video telephony and data, it is possible to use another known manner of operating telecommunications networks in the region of an end exchange wherein the transmission of subscriber addresses is obviated, for example, as disclosed in the German published application No. 2,438,199, corresponding to U.S. Pat. No. 4,051,328.
In this known process, from an end exchange which has outgoing T.D.M. lines and incoming T.D.M. lines, the items of telecommunications information for subscriber end stations participating in connections of a T.D.M. line are transmitted in the sequence of their connection to the T.D.M. line. At the beginning of each sampling pulse frame, the participating subscriber end stations are rendered ready for reception, but are continuously blocked from receiving items of telecommunications information transmitted by other subscriber end stations. Following the first reception and transmission of the items of telecommunications information which they are to transmit in the ongoing direction, the individual subscriber end stations are blocked from receiving further items of telecommunications information emanating from the exchange, in which they allow these items of information to pass through. Therefore, the allocation of the items of information to individual subscriber end stations is carried out on the basis of the sequence in which the items of information occur on the transmission line.